1. Field of the Invention
The present invention relates to a light emitting device using a light emitting diode (LED), and more particularly, to a side-view type light emitting device that can uniformly emit light according to its positions and a line light source type light emitting device having a novel structure and using the LED with a point light source characteristic.
2. Description of the Related Art
In general, a light emitting diode (LED) is provided in a form of a light emitting device including a package body provided with a lead frame to which an electrode is connected. The LED may be coupled to various light receiving devices such as a backlight unit (BLU) of a liquid crystal display (LCD), a light guide plate of a surface light emitting display, and an optical sensor, and thus the LED is being used in various application fields.
Specifically, a side-view type light emitting device that is one type of the light emitting device is being widely used as a light source for the BLU of the LCD.
With the increasing tendency toward a large-scale BLU, light uniformity of the large-scale BLU must be maintained over the entire panel in spite of their large area. However, since an LED light source used as a BLU light source is a point light source, the LED light source has a disadvantage in terms of the light uniformity when compared to a related art cold cathode fluorescent lamp (CCFL) that is a line light source.
The LED is being used in the various application fields because the LED may be coupled to the light receiving devices (the BLU of the LCD, the light guide plate of the surface light emitting display, the optical sensor, etc). In such an application field, the LED has a great disadvantage in that it is difficult to realize the line light source because the LED acts as the point light source.
FIG. 1 is a graph illustrating measurement results of an output distribution of light emitted from a light emitting surface LP of a related art side-view type light emitting device 1.
Referring to FIG. 1, a light output intensity is highest at a central portion (an upper side of an LED chip 5) of the light emitting device 1. The light output intensity gradually decreases toward sidewall directions of the LED chip 5, and then the light output intensity increases again a little at portions adjacent to the sidewalls.
Since the LED chip 5 is disposed at a central portion of a package to condense light emitted from the LED chip 5 into a direct upper side of the LED chip 5, the light output intensity is highest at the central portion of the light emitting device 1. Also, since light distributed over side surfaces of the LED chip 5 or light diffused into the LED chip 5 is reflected from the sidewalls of a package body to emit the reflected light into the outside, the light output intensity increases in the sidewall regions. Accordingly, the light output intensity greatly depends upon reflectance and inclination of the package body.
As describe above, the side-view type light emitting device has a point light source characteristic in which an LED chip region is bright. Thus, in case where the side-view type light emitting device is applied to a light guiding panel of a BLU, the side-view type light emitting device has a hot spot region in which light brightly shines at a central portion of an LED and a dark spot region that is a dark region between the LED chips. Thus, due to such a point light source characteristic, the overall light emitting uniformity significantly decreases.